John Curl's Blowtorch preamplifier part II

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Well you've got me confused again. The eye diagram on a typical audio link is orders of magnitude beyond that needed for even one dropped bit per cd.

Scott,

I have reports of folks hearing differences on a specific chip when used in two different start up methods. Measurements show there is a difference of less than 40 nS jitter. Folks report various fiber links sound different, Measurements show there are also nanosecond level jitter changes. Now would I expect those changes in jitter to matter on an AES/EBU SPIDF data stream? NO!

Since I can design better than that I will.

My current system with some of the modules measures better than my reference 25' Rapco/Horizon Microphone cable. (Some measure worse but we are talking +/- 20%) Now should I add a chip that in my usage will make that 10 times worse? Should I use the higher loss fiber and connectors that show increased jitter? Of course not, even if there were no reports by listeners.

I am in the design phase of the system and looking at measurements. Next month or so enough will be built we can listen to stuff.

Now that is the data I have measured.

The real issues are am I measuring what actually counts and are my instruments reading correctly. (I suspect my AP is not reading the errors correctly! So I will be comparing it to another make of gear.)

Now the AES system is used with great success by many. The other approaches that are popular in the arena market, clearly have some limits. Newer products have been introduced that address those issues, but are not as widely available and still make what I consider mistakes in fundamental design philosophy for my application.

Now I have done the designs, built the prototypes, measured them, made needed changes and am now finishing up assembling what should be the final system. Delivery of parts begins in April, so I should have an adequate time margin to be sure it really does what it should.

Will I be able to hear a difference? I would be surprised if it didn't make one. Would that be due to 25 nS of jitter, well the reason why I did it was to decrease group delay and group timing differences. So I do expect a change for the better.

Group delay differences hurts when you have overlap between two loudspeakers fed from different DSP units. When the delay is not stable you get very annoying artifacts.

Now would you allow an extra 25 nS of jitter when there is zero material or field labor cost increase?

Now when folks reclock their CD's my OPINION is that there is some improvement due to a more stable final clock. Is it the best way to play CD's? My OPINION is that there are better approaches. However there really are times when you want to do digital transport of audio signals in real time and those issues have much in common with many folks' CD reproduction systems.

No more, no less.

BTY in my kind of systems the music files are almost always stored on a computer.
 
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Scott,
If you have a device that has a rising rate impedance and also has more than a purely resistive impedance curve you will never reproduce those frequencies correctly. Phase shifting is going to destroy those tones. We need to have a perfectly flat impedance curve, time coherent zero phase shift and flat frequency response. Only then can we produce those upper frequencies with any accuracy. It doesn't matter now good you get the electronic chain before the loudspeaker if you can't reproduce a coherent waveform from the loudspeakers, you are only chasing fairy dust then.

Yes the same applies to both sides. You see my point, the frequency response of that mic indicates that it might not be able to capture a coherent wave front.

jcx - I don't think that is exactly what he meant. I haven't computed them but I don't think the group delay characteristics of that mic are all that great at the high end.
 
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Scott,

I have reports of folks hearing differences on a specific chip when used in two different start up methods. Measurements show there is a difference of less than 40 nS jitter. Folks report various fiber links sound different, Measurements show there are also nanosecond level jitter changes. Now would I expect those changes in jitter to matter on an AES/EBU SPIDF data stream? NO!

I don't chase these anecdotal results, waste of time.
 
I don't chase these anecdotal results, waste of time.

I know it is just a coincidence that things that seem unreasonable surprisingly have a correlation with measurements. I suspect that the jitter measurement is just another symptom of a problem that I am not measuring correctly.

BTY never feed the circus tigers by hand. I am told by many anecdotally, it is not a good idea!
 
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I know it is just a coincidence that things that seem unreasonable surprisingly have a correlation with measurements. I suspect that the jitter measurement is just another symptom of a problem that I am not measuring correctly.

Same with resistors I guess, except if I spent the time doing an exhastive search I would find by anecdote that there is no preference to any particular brand, measurements not withstanding.
 
jcx,
Sorry if I sometimes mix up terms here. Yes Timbre, if you can't tell a cymbal from a triangle is the fact that the frequency response is correct mean that the reproduction of the original waveform is correct? I rather think not. And yes I can hear the difference between those two things if they are recorded correctly.
 
Scott, at last fame and adulation as befits someone with our Lord JC's blessing

Even though its obvious he didn't even read the 1st article. Maybe he didn't read those B&K & AES articles either. Did he really explain kT/C to Harry Nyquist?
Come on Richard, as a friend, lighten it up a little. Let's all have a happy holiday season.
Du.uuh! Inscwutable Owiental FAILS in attempt at decadent Western humour! :eek:
 
jcx,
Sorry if I sometimes mix up terms here. Yes Timbre, if you can't tell a cymbal from a triangle is the fact that the frequency response is correct mean that the reproduction of the original waveform is correct? I rather think not. And yes I can hear the difference between those two things if they are recorded correctly.
Interesting question. The dynamic power evolution + harmonic composition ?
 
I totally agree, quite often something fundamental is missing in existing recordings but the >20kHz thing might be useful in making a system better althought it can already work quite good without this extension in frequency range.
I'll do this in big letters this time: THIS IS AN ISSUE WITH THE REPRODUCTION ELECTRONICS. It is not in the recording, it is not a problem of speaker drivers, it is distortion of the playback chain, specifically electrical in nature. Why am I sure? Because I have heard recordings that sound miserable, dead as a dodo, lifeless, not worth a cracker, on other systems ... come completely to life when reproduced correctly! Even ultra cheap systems can make it happen, if they are fully sorted out!

Again, it is about reproducing loudness with subjectively inaudible distortion, which translates in the listener's brain as intensity of sound, which is what all real musical instruments do easily, that's the signature of the real thing. And it is most certainly possible to get audio systems to do that, I've been playing with this "problem" for the last 25 years ... ;)

Frank
 
... but the >20kHz thing might be useful in making a system better althought it can already work quite good without this extension in frequency range.
Err.rrh! The results of loadsa Blind Listening Tests show conclusively that restricting the bandwidth on MUSIC SOUNDS BETTER. :eek:

But doing this makes certain supa dupa measurements look bad.

Of course if the supa dupa measurements and your BELIEFS are more important than the sound, you can ignore all these evil Blind Listening Tests on the perfectly valid grounds that they don't agree with your BELIEFS.

The Church has precedent for this dating back to at least Galileo.

the Meyer & Moran experiment is unfortunately not an example of good scientific practice and it should not have passed the review board.
Err.rrh! Meyer & Moran has probably been subject to greater scientific scrutiny than any other audio experiment in recent history.

Admittedly, it does not have the absoluteness of Harry Olson but for its expressed purpose, to investigate the effect of evil Red Book CD processing on pristine SACD stuff, its a pretty watertight case of 'good scientific practice'.

That's not to say it's perfect. I have loadsa criticisms but none of them affect their conclusion.

Would you care to suggest a recent experiment with different results that you BELIEVE illustrates 'good scientific practice'?
 
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supersonics and Meyer & Moran

Meyer & Moran details from Boston Audio Soc. including list of SACDs

Thanks for this link, Waly.

Anyone have comments on their list of SACDs .. especially on the presence or absence of supersonics?

I note only one Telarc; SACD 3488. Pavel, is it on your vintage supa dupa Telarc list?
________________

Every 10yrs or so, I have a yen to repeat certain audio experiments I've conducted in Jurassic times on the grounds that new supa dupa tech must make stuff audible which wouldn't have have been audible before.

I encountered very few instances of changed audibility, eg 'audibility of Phase Mucking Up on 'music'. :mad:

I'm seriously overdue on my next round. The tech has made huge jumps while I was a beach bum. We now have computing power I only dreamed about in the last millenium. I have managed to crudely harness some of this in the design of SOTA mikes. The quality of recording gear available at low cost is incredible (though there is loadsa rubbish around.)

I no longer have the resources of a competent R&D Dept, purpose built Listening Room, Golden Pinnae gear, ABC box etc to conduct pukka Double Blind Listening Tests but I'm still interested in having a go with my aging pinnae :)
 
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